THE NAKED APE

Aggressive hair-erection has led to the growth of specialised regions such
as crests, capes, manes and fringes. These and other localised hair patches
have become highly conspicuous. The hairs have become elongated or stiffened.
Their pigmentation has often been drastically modified to produce areas of
strong contrast with the surrounding fur. When aggressively aroused, with the
hairs standing on end, the animal suddenly appears larger and more
frightening, and the display patches become bigger and brighter.
Aggressive sweating has become another source of scent-signals. In many
cases there have, once again, been specialised evolutionary trends exploiting
this possibility. Certain of the sweat glands have become enormously enlarged
as complex scent-glands. These can be found on the faces, feet, tails and
various parts of the body of many species.
All these improvements have enriched the communication systems of animals
and rendered their mood language more subtle and informative. They make the
threatening behaviour of the aroused animal more `readable' in more precise
terms.
But this is only half the story. We have been considering only the autonomic
signals. In addition to all these there is another whole range of signals
available, which stem from the tensed-up muscular movements and postures of
the threatening animal. All that the autonomic system did was to gear the
body up ready for muscular action. But what did the muscles do about it? They
were stiffened for the onslaught, but no onslaught came. The outcome of this
situation is a series of aggressive intention movements, ambivalent actions,
and conflict postures. The impulses to attack and to flee pull the body this
way and that. It lunges forward, pulls back, twists sideways, crouches down,
leaps up, leans in, tilts away. As soon as the urge to attack gets the upper
hand, the impulse to flee immediately countermands the order. Every move to
withdraw is checked by a move to attack. During the course of evolution this
general agitation has become modified into specialise postures of threat and
intimidation. The intention movements have become stylised, the ambivalent
jerkings have become 134